Variable resistance component



Jan. 9, 1968 v JOY 3,363,212

VARIABLE RESISTANCE COMPONENT Filed Sept. 9, 1965 INVENTOR ALDEN .JvV

ATTORNEYS United States Patent ABSTRAT OF THE DISCLOSURE A carbon potentiometer in which means are provided for rotating a contact member about a first electrical contact projection on the contact member in engagement with a contact surface so that a second contact projection on the contact member can sweep over and in engagement with a resistance element and in which an access end of a casing is provided with a central opening and a portion forming a stationary stop and a portion of the contact member projects within the access providing a rotating stop which upon abutting the stationary stop prevents further rotation of the contact member.

A variable resistance component constructed in accordance with the teachings of this invention and the method of using the same is described herein with reference to the drawings in which:

FIG. 1 is an exploded perspective view of a variable resistance component constructed in accordance with the teachings of this invention with the base thereof absent;

FIG. 2 is a longitudinal sectional view of the variable resistance component in assembled condition; and

FIG. 3 is a partially sectional view taken along the line 33 in the direction of the arrows, as seen in FIG. 2.

Summary of the invention A variable resistance component including in combination a cylindrical base, a surface of said base, a conducting element supported by said base at said surface, a carbon resistance element supported by said base at said surface in circular disposition concentric with said conducting element and electrically insulated therefrom, a cylindrical contact member, a base of said contact member facing said surface, first and second spaced contacts integral with said contact member and projecting therefrom toward said surface with said first contact centrally located of said base, a cylindrical casing having an open base end and a partially closed access end, said base end of said casing being attached to said base with said contact member disposed therein, a circular-tract formed on the inner surface of said partially closed access end, a spring member formed of resilient metal disposed between said contact member and said partially closed access end with a first portion thereof engaging said contact member and constrained from rotary motion with respect thereto, and a second portion thereof yieldingly urged against said track whereby said first and second contacts are yieldingly urged respectively against said contact element and said resistance element, means terminating said contact element and said resistance element, a screwdriver receiving slot formed in said spring member, a central opening in said partially closed access end of said casing exposing said slot whereby said second contact member can be rotated to sweep over and in engagement with said resistance element, a portion of said access end of said casing projecting within said central opening providing a stationary stop and a portion of said spring member projecting within said opening providing a rotating stop which upon abutting said stationary stop prevents further rotation of said contact member.

The variable resistance component disclosed herein is a hot molded composition carbon potentiometer consist- Patented Jan. 9, 1968 ing of a cover 10, spring support 11, carbon contact brush 12 and base 13 supporting terminal members 14 and 15 and carbon track 16.

The cover is cylindrical and formed of brass or any other suitable material with pins 17, 18, 19 and 20 projecting longitudinally in the direction of base 13. A circular access opening 21 is formed in the cover to permit the insertion thereof of the end of a screw driver for varying the resistance of the unit.

The movable contact member is a carbon button 12 which can be processed of conductive composition in any suitable manner. The button is provided with a contact portion 22 which projects from surface 23 in the direction of the base and is also provided in surface 23 with a centrally located raised portion 24, the purpose of which will be explained below. The remaining face surface is indicated in the figures by the numeral 25 and has formed therein a rectangular slot 26 which is centrally located to receive the end of a screw driver.

Spring support 11 is formed of a suitable spring material such as beryllium copper. The spring member 11 is attached to button 12 by means of lugs 27 and 28 recieved within channels 29 and 30 respectively cut out of button 12. The base in each of channels 29 and 30 is provided with a flat maximum depth section nearest base 13 and a flat minimum depth section nearest spring 11 with an intermediate planar surface connecting these two sections. Each of the lugs is notched such as, for example, lug 27 is notched inwardly at 31 and lug 28 is notched inwardly at 32, so that the button 12 and spring member 11 can be joined by a snap action when lugs 27 and 28 are inserted respectively in channels 29 and 31).

Legs 33 and 34 supporting respectively mechanical contact buttons 35 and 36 project toward cover 10 so that buttons 35 and 36 ride upon the inner surface 37 of the cover yieldingly urging the contact button 12 toward base- 13 and projecting electrical contact 22 against arcuately formed carbon contact track 16 supported in base 127 Button 24 is yieldingly urged against conductive island 38 which is an extension of terminal 14 and supported centrally in base 13 and disposed in the same place as the carbon element 16 is disposed. Although island 38 is shown integral with terminal 14 it need not be and can be formed of any suitable conductor. Terminal member 15 is electrically connected at one end of carbon contact track 16 and terminal 14 is electrically connected to island 38 so that there is electrical continuity between terminals 14 and 15 through island 38, raised portion 24- of button 12, and carbon track 16.

Spring member 11 is provided with opening 39 which allows a screw driver to pass from opening 21 in cover 10 to engage slot 26 in button 12 to allow the rotation of the button 12 and spring 11 combination allowing contact 22 to wipe over the carbon track 16 varying the resistance appearing between terminals 14 and 15.

Mechanical contacts 35 and 36 during rotation of but ton 12 wipe surface 37 of cover 10 and upwardly projecting lug portion 40 is provided to contact radially inwardly directed cover portion 41 providing a positive stop at the desired location.

In assembly the base is formed including carbon track 16 and island 38 together with terminal members 14 and 15-. The contact button 12 is formed separately, as is spring member 11 in cover 10. The spring member and button 12 are then assembled as a unit by the snapping of lugs 27 and 23 within channels 29 and 30 and the combination of spring and button disposed within cover 10 which then receives the base assembly and the lugs 17, 18, 19 and 20 are turned over about the bottom of base assembly 13.

Thus, among others, the several objects in the invention as specifically aforenoted, are achieved. Obviously,

numerous changes in construction and rearrangement of parts may be resorted to Without departing from the spirit of the invention as defined by the claim.

I claim:

1. A variable resistance component including in com- 'bination a cylindrical base, a surface of said base, a conducting element supported by said base at said surface, a carbon resistance element supported by said base at said surface in circular disposition concentric with said conducting element and electrically insulated therefrom, a cylindrical contact member, a base of said contact member facing said surface, first and second spaced contacts integral with said contact member and projecting therefrom toward said surface with said first contact centrally located of said base, a cylindrical casing having an open base end and a partially closed access end, said base end of said casing being attached to said base with said contact member disposed therein, a circular track formed on the inner surface of said partially closed access end, a spring member formed of resilient metal disposed between said contact member and said partially closed access end with a first portion thereof engaging said contact member and constrained from rotary motion with respect thereto, and a second portion thereof yieldingly urged against said track whereby said first and said second contacts 25 J. G. SMITH, Assistant Examiner.

are yieldingly urged respectively against said contact element and said resistance element, means terminating said contact element and said resistance element, a screwdriver receiving slot formed in said spring member, a central opening in said partially closed access end of said casing exposing said slot whereby said second contact member can be rotated to sweep over and in engagement with said resistance element, a portion of said access end of said casing projecting within said central opening providing a stationary stop and a portion of said spring member projecting within said opening providing a rotating stop which upon abutting said stationary stop prevents further rotation of said contact member.

References Cited RICHARD M. WOOD, Primary Examiner. 

